1. The article is overly lengthy; it is suggested that the author shorten it. For example, condense the introduction to focus more on the study's specific objectives and significance. Reduce background information that isn't directly relevant to your study's aims.
2. Explain the rationale for choosing specific organic salts.
3. Provide more details about the relative humidity control and measurement, such as the precision and accuracy of RH measurements.
4. It is suggested to add some summary tables comparing the phase transition behaviors of different organic salts and ammonium salts.
5. What is the potential impact of temperature on phase transitions? What is the relationship between liquid-liquid phase separation and phase transition behaviors in this study? It is suggested to discuss them in the implication.
6. Ensure all references are up-to-date and relevant. Check if any recent studies on similar topics have been published and could be included. E.g. recent field observation studies have highlighted the significant role of organic acids in modifying the phase behavior of ammonium sulfate aerosols, further complicating the prediction of aerosol phase states (Li et al., EST, 2021, 55, 16339; Yuan et al., 2023, ACP, 23, 9385; Kirpes et al., PNAS, 2022, 119, 14).
7. Specific comments:

Abstract: The abstract is informative but could be improved by including a brief mention of the methodology (ATR-FTIR spectroscopy) and the key findings related to the RH ranges.

Line 14: A detailed introduction to “aqueous replacement reactions” for better understanding the mechanisms.

Line 16: 35.7%~12.7%, 64% and 65.5%~60.1% RH?

Figure 1: Enhance the figure with annotations indicating key RH ranges where phase changes occur.

Figure 7: Include a scale bar in each image to indicate the size of the observed particles. Highlight key features in the images, such as the appearance of solid entities or changes in particle morphology, with arrows or labels.